The present invention relates to a process for the production of a braking band of a brake disk with ventilation ducts and to a braking band produced by this process.
In particular, the present invention relates to a process for the production of a braking band having ventilation ducts and made of a ceramic material such as, for example, C/SiC.
The ventilation ducts of braking bands which are currently commercially available are generally produced by various methods.
A first method provides for the moulding of the braking band as a solid body and the subsequent formation of radial and non-radial holes lying in the central plane of the thickness of the band and constituting the ventilation ducts.
A second method for the production of braking bands of ceramic material for a brake disk with ventilation ducts provides, in a first step, for the separate moulding of two reflectively symmetrical portions of the braking band, which have channels within their respective surfaces that face one another. The two portions are then brought into contact and joined together to form the finished band in which the channels of each of the portions together define the ventilation ducts.
In a third method, the ventilation ducts are produced by means of a core of ceramic material which is inserted in the mould, between two layers of the material for forming the band, and which already has in its interior the cavities which will constitute the ventilation ducts. Since it is made of material identical or at least similar to that of the band, the core becomes closely connected to the ceramic material of the braking band, forming a ceramic “sandwich” structure therewith. The core itself is formed by two half-cores arranged facing one another and joined together in a similar manner to that described for the braking band of the above-mentioned second production method.
However, the above-mentioned methods have some problems and disadvantages connected mainly with technological difficulties.
In the first method, the formation of the holes in the thickness of the braking bands is in fact very expensive and difficult because of the hardness of the materials used. Moreover, the machining inside the braking band is much less controllable than the external machining of the band. During this machining, it is consequently not possible to exclude the formation of sharp edges or even cracks, which cannot be tolerated in the production of a braking band.
The second method, on the other hand, has the disadvantage of the need to join together two portions of a braking band which, since they are moulded separately, may not correspond and may therefore fit together unevenly. This could give rise to a product in which dangerous detachment of these two portions due to non-symmetrical forces can easily occur.
With regard to the third method, this requires the provision of two moulds for the moulding of the respective half-cores, as well as a third mould for the moulding of the braking band. Moreover, in order to achieve satisfactory results, the core produced by means of the two half-cores has to be positioned very accurately inside the mould for moulding the braking band. All of this requires quite complex techniques as well as manual intervention in every moulding cycle. The above-mentioned technological complexities, as well as the resulting costs, also reduce the competitiveness of brake disks of ceramic material with ventilation ducts, in comparison with non-ventilated disks.
There is consequently a need to provide a process for the production of braking bands with ventilation ducts which is particularly easy to implement and economical.